Investment in Leasing Operations: Credit Losses (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020	Dec. 26, 2020
Activity in the allowance for credit losses for leasing operations
Balance at beginning of period			$ 270,200	$ 580,600
Provisions for credit losses	$ (55,900)	$ (339,600)	(167,300)	164,300
Recoveries				(12,400)
Deductions for amounts written-off				(148,900)
Balance at end of period	102,900	$ 583,600	102,900	$ 583,600
Investment In Leases
Total investment in direct financing and sales-type leases	5,080,800		5,080,800		$ 13,512,300
Allowance for Credit Losses
Total	102,900		102,900		270,200
Investment in leases
Investment In Leases
Collectively evaluated for loss potential	5,080,800		5,080,800		13,512,300
Total investment in direct financing and sales-type leases	5,080,800		5,080,800		13,512,300
Allowance for Credit Losses
Collectively evaluated for loss potential	102,900		102,900		270,200
Total	$ 102,900		$ 102,900		$ 270,200